Method for producing plasterboard with four tapered edges

ABSTRACT

The invention relates to a method of producing plaster boards ( 12 ) in which two bound sheets of paper, namely one cream paper ( 3 ) and one grey paper ( 4 ), enclose a plaster-based hydraulic binder ( 2 ) in a former ( 7 ), thereby creating a composite strip ( 10 ) which hardens on two hardening strips ( 8  and  9 ), said strips having two horizontal tapering strips disposed along the edge thereof. The invention consists in: shaping the cream paper ( 3 ) along emboss lines ( 20 ); providing stiffening slots ( 23 ) on either side of the emboss lines ( 20 ); reinforcing the mechanical strength of said emboss lines ( 20 ) by covering same with a coating ( 15 ); allowing the emboss lines ( 20 ) to exceed the aforementioned former ( 7 ) and the hardening strips ( 8  and  9 ) and generating the double slope imprint ( 19 ); and, subsequently, cutting the composite strip ( 10 ) to the right and at the middle of each double slope imprint ( 19 ).

BACKGROUND OF THE INVENTION

The present invention relates to a method and apparatus for producingplasterboard with four tapered edges at the outer edge of each board.

The invention is in the field of continuous plasterboard production inwhich two sheets of cardboard-type paper, the lower one of which,because of its color is called the cream or facing paper (hereinafterthe facing paper) and the other upper one being called the gray orbacking paper are unrolled and come to enclose a plaster-based hydraulicbinder inside a shaping means in the form of shaping plates or shapingrollers.

These two sheets of paper constitute, with the hydraulic binder, acomposite strip which generally hardens on two hardening belts at theedges of which two narrow taper reservation strips are present allowingthe future board to be provided with longitudinal tapered edges.

This composite strip is cut to the desired length, passed through thedrying oven and is finally recut to its definitive length before beingstacked. Such a method is well-known and will not be described furtherin detail in this specification.

The value of having tapered edges all around plasterboard has been knownand appreciated for many years. Indeed, they facilitate the abutment andjointing of plasterboard and allow large surface area constructions tobe built with excellent flatness characteristics and mechanicalstrength.

For many years now, it is known how to produce plasterboard with taperedlongitudinal edges on continuous manufacturing lines but there is nomethod allowing production, on such continuous operating lines, ofplasterboard with transverse tapered edges having the samecharacteristics as the longitudinal tapered edges.

There have obviously been numerous attempts and numerous patents havebeen taken out, essentially U.S. patents, attempting to resolve thisproblem of continuous production of tapered transverse edges. U.S. Pat.No. 2,238,017 in particular attempted, in 1941, to create excessthickness by bending of cardboard but this invention never went intoindustrial development probably because the bending did not withstandthe tension in the paper or the weight of the hydraulic binder.

It must be recognized that currently, plasterboard with taperedtransverse edges if boards do exist are either the result of machiningof the edges called tapering or feathering or artifices such asgrooving, pressing and bonding of the edge, or, more frequently, areprovided by the artisan who simply planes the edge of the board toprovide a transverse taper.

These solutions are all expensive in terms of cost of producing theboard and moreover the qualities of the transverse taper thus realizedare far from those of the longitudinal taper. Today both the market andindustry have really high expectations as regards this situation.

SUMMARY OF THE INVENTION

The method and its apparatus according to the invention allow thesedisadvantages to be overcome.

A solution to the problem posed is according to the invention aproduction line of the type presented in the introduction, whichconsists of:

embossing the facing paper on-the-fly along the lines of protuberancestransverse and perpendicular to the direction of unwinding of saidfacing paper.

reinforcing, on-the-fly, the mechanical strength of these protuberancesalong two notch lines arranged either side of the latter,

reinforcing, on-the-fly, the mechanical strength of these protuberancesby means of a hardening coating, sprayed inside and around the latter,

repeating these lines of protuberances on the facing paper, at a precisestep,

allowing these lines of protuberances projecting approximately 1.5 mmbelow the facing paper to cross the former and the hardening belts,

cutting the composite strip with the shears right in the middle of theimprint left by the line of protuberances during the embossing, andhardening of the composite band.

The result is a novel production method and apparatus whichsatisfactorily address the problem posed, the transverse tapersresulting from the imprints having surface appearance, shape andstrength qualities identical to those of longitudinal tapers and beingsatisfactorily produced using a continuous method which proves to bevery cheap and very attractive to the plaster board industry and market.

The description and FIGS. below represent an example of producingplaster-based board-bound plates showing the particular advantages ofthe invention as mentioned previously, but without being limiting: otherproduction methods are possible within the scope and extent of theinvention, in particular the production of plaster boards usingmineral-based papers or glass mats instead of cardboard-type papers ormore generally the production of plates using two sheets or an envelopeenclosing, after passing into a former, a drying hydraulic binder.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the head of the production line in which the novel methodof the invention is used.

FIG. 1 a shows, according to the invention, in side view and enlargedthe line of protuberances just before it passes below the mixer.

FIG. 1 b shows, according to the invention, in side view and enlargedthe line of protuberances just after it has passed below the mixer andbefore it passes into the former.

FIG. 1 c shows, according to the invention, in side view and enlargedthe line of protuberances just after it has passed into the former andduring its passage over the hardening belts.

FIG. 1 d shows, according to the invention, in side view and enlargedthe line of protuberances leaving the hardening belts and before theshear cut.

FIG. 1 e shows according to the invention, in side view and enlarged theline of protuberances just after the shear cut.

FIG. 2 shows a plaster board with 4 tapered edges that has been producedwith the method of the invention.

FIG. 3 shows the apparatus according to the invention for berthing thefacing paper and realizing the lines of protuberances.

FIG. 4 shows the view along F of the apparatus of FIG. 3.

FIG. 5 shows, according to the invention, the facing paper seen frombelow, as machined after it has crossed the apparatus of FIGS. 3 and 4.

FIG. 6 shows, according to the invention, the section and perspectiveview SS′RR′ of the facing paper of FIG. 5.

FIG. 7 shows, according to the invention, the side and section view ofthe facing paper at the line of protuberances before it passes below themixer.

FIG. 8 shows, according to the invention, the side and section view ofthe composite strip at the line of protuberances after it has passedinto the former.

FIGS. 9 and 10 show, according to the invention, the side and sectionview of the composite strip at the line of protuberances immediatelyafter the cutting operation.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows a continuous production line for plaster board (12), of thetype described in the introduction, in which two sheets ofcardboard-type paper, a lower one constituting facing paper (3) and anupper gray or backing paper (4), unwind and enclose in a former (7) ahydraulic binder (2) coming from a mixer (1). These two sheets ofcardboard-type paper, cream (3) and gray (4) constitute with thehydraulic binder (2) a composite strip (10) which hardens on the twohardening belts (8) and (9). These two hardening belts (8) and (9) haveat their edges two small tapered strips which will create thelongitudinal tapers (13) on the composite strip (10). The compositestrip (10) is cut to length l by the shears (11), the resulting plasterboards (12) are provided with longitudinal tapers (13) but are notprovided with transverse tapers (14).

The method according to the invention allows precisely the continuouscreation of transverse tapers (14) as well as longitudinal tapers (13)on the plaster boards (12) leaving the shears (11).

According to the method of the invention, the first stage consists ofcreating an extra thickness below the facing paper (3) before the latterpasses below the mixer (1) and before it crosses the former (7). Tocreate this extra thickness of approximately 1.5 mm below the facingpaper (3), the said facing paper (3) will be stamped along the lines ofprotuberances (20).

According to the invention, these lines of protuberances (20) arestraight lines of a length less than the width of the facing paper (3)centered and perpendicular to the direction of unwinding of the saidfacing paper (3). The protuberances (16) of these lines of protuberances(20) are spaced approximately 20 mm apart and project approximately 1.5mm below the facing paper (3), this value of 1.5 mm corresponding to thegenerally sought value of the transverse taper height “b” (29).

These lines of protuberances (20) are provided below the facing paper(3) on-the-fly, at a rate that can be less than two seconds and conformto a precise step “p” (48). This step “p” (48) depends on the soughtlength of the plaster board (12), the longitudinal expansion of thecomposite strip (10) during its hardening on the hardening belts (8) and(9) and the excess length necessary for the sawing of the plaster boards(12) on leaving the line. This is an interval or step “p” (48) that aperson skilled in the art can easily calculate.

According to the method of the invention, these lines, discontinuous bydefinition, of protuberances (20) have the very unusual advantage thatthey do not disappear or fade under the mechanical tension “T” (47) ofthe facing paper (3) unlike other devised methods which consist offolding or embossing the facing paper (3) along a continuous profile andover a large width.

The method of the invention, simultaneously with the embossing of thelines of protuberances (20), notches the facing paper (3) along twolines of reinforcement notches (23). These lines of reinforcementnotches (23) are realized on the outside of the facing paper (3) oneither side of each line of protuberances (20) of the same length as thelines of protuberances (20) parallel and centered to the lines ofprotuberances (20). The function of these two lines of reinforcementnotches is to reinforce, helping the line of protuberances (20) tosupport the weight of the hydraulic binder (2) in subsequent stages ofthe method.

According to a variant of the method of the invention, the length “l”(49) of the lines of protuberances (20) is equal to the width around allof the plaster board (12) minus the sum of the widths of the twolongitudinal tapers (13).

The method according to the invention then consists, in the zone betweenthe forming table (5) and the former (7), of protecting the lines ofprotuberances (20) against pulling out, catching or deformation. Forthis, in the said zone all the rough sections, all the catch points (17)are removed, and grooves are arranged on the spreader (6). Thus equippedwith grooves, the said, generally vibrating or rotating, spreader (6)shakes the facing paper (3) and the hydraulic binder (2) withoutaffecting the protuberances which pass without contact in the recess ofits grooves, i.e. without contact with said spreader (6).

According to the method of the invention, as the lines of protuberances(20) cross the former (7) they raise the facing paper (3) locally andreduce accordingly the quantity of hydraulic binder (2) contained in thecomposite strip (10), thus the upper surface of the composite strip (10)leaving the former (7) will be uniformly flat despite the locally raisedsections of the latter.

According to the method of the invention, the lines of protuberances(20) projecting below the facing paper (3) keep the composite strip (10)raised until it is completely hardened.

According to the method of the invention, on leaving the hardening belt(9) the composite strip (10) has on its lower surface double-slopeimprints (19) spaced apart at a distance slightly greater than thelength of the plaster boards (12) to be produced.

The method according to the invention consists in the last phase ofcutting the composite strip (10) using the shears (11) at the level, inthe center and in the axis of each of the double-slope imprints (19).

The result, at this stage of the method according to the invention, is aplaster board (12) with 4 tapered edges at its periphery, twotraditional longitudinal tapers (13) and two transverse tapers (14)created by the method according to the invention. This plaster board(12) then crosses the drier and is sawn to length, this sawing causingthe residual 1/2 lines of protuberances (50) to disappear completely.The plaster boards (12) provided with tapers over the whole of theirperiphery are stacked and then rejoin the factory stock.

According to a variant of the method of the invention, the cutting withthe shears (11) occurs simultaneously in the double-slope imprints (19)and at an equal distance from two double-slope imprints (19), theplaster boards (12) thus produced having 3 tapers, two longitudinaltapers (13) and one transverse taper (14), these plates with 3 tapersbeing useful for particular market applications.

According to a variant of the method of the invention, the insidesurface of the protuberances (16), the inside of the bottoms of theprotuberances (22), as well as the upper and horizontal surfaces of thefacing paper (3) situated between the protuberances (16) and thereinforcement notches (23), also called reinforced surface (21), arecovered with a coating (15). This on-the-fly application of the coating(15) is realized immediately after the embossing operation of the linesof protuberances (20). The chemical composition of this coating (15) issuch that with almost immediate effect it allows the mechanical strengthof the protuberances (16) to be increased, the lines of protuberances(20) to be made impermeable and protected against softening, said linesof protuberances (20) to be made tight vis-à-vis the hydraulic binder(2), and finally a good bonding of the hydraulic binder (2) and thefacing paper (3) on the reinforced surface (21) to be guaranteed.

According to another variant of the method of the invention and in orderto achieve a good geometric connection of the transverse tapers (14) andthe longitudinal tapers (13) on the plaster board (12), the lines ofprotuberances (20) are extended at each end over a length equal to thewidth of the longitudinal tapers (13). This extension of the line ofprotuberances (28) consists of protuberances (16) the depth of whichdecreases as the said extension of the line of protuberances (28)approaches the outside edge of the facing paper (3). This extension ofthe line of protuberances (28), when crossing the hardening belts (8)and (9), comes to rest on the tapered strips which serve to make up thelongitudinal tapers (13).

According to a variant of the method of the invention the shape of theprotuberances (16) created by embossing is adapted so that the latterhave the best possible mechanical characteristics, and can equally wellbe of hemispherical, pyramidal, conical or half-moon shape without beinglimited to these.

According to a variant of the method of the invention, the facing paper(3) is marked at the start of its transverse taper (14) with a lightnotching, this line marking the start of the transverse taper (14)improving both the geometry and the attractiveness of the transversetaper (14). This line marking the start of the transverse taper (24) isthe same length as and parallel to the line of protuberances (20) and isnaturally situated vis-à-vis the latter at a distance equal to the widthof the transverse taper “a” (27). This line marking the start of thetransverse taper (24) through a light notching of the facing paper (3)either outside or inside the latter is realized simultaneously with theembossing of the lines of protuberances (20).

According to a variant of the method of the invention, the facing paper(3) is marked on the line connecting the transverse taper (14) and thelongitudinal taper (13). This tapers connection line (26) links the endof the line marking the start of the transverse notch (14) to the end ofthe line of reinforcement notches (23). This tapers connection line (26)naturally forms an angle “c” (46) of 45° to the main axes of thetransverse tapers (14) and longitudinal tapers (13). This tapersconnection line (26) improves both the geometry and the attractivenessof the zone where the transverse taper (14) and the longitudinal taper(13) meet. This tapers connection line (26) which involves a lightnotching of the facing paper (3) either outside or inside the latter isrealized simultaneously with the embossing of the lines of protuberances(20).

According to a variant of the method of the invention, the outsidesurface of the facing paper (3) corresponding to the future transversetaper (14) is roughened in order to promote the bonding of the jointingcoating which will be applied later in this zone when using the plasterboard (12). This rough surface (25) corresponding to polygons defined bythe line of reinforcement notches (23), the line marking the start ofthe transverse taper (24) and the two tapers connection lines isobtained by pricking, knurling, embossing or chafing said surface. Thisstage of the method according to the invention of realizing the roughsurfaces (25) occurs at the same time as the embossing of the lines ofprotuberances (20).

According to the method of the invention, the transverse taper height“b” (29) and transverse taper width “a” (27) are regulated by adjustingthe following parameters:

the protuberances height “h” (45) by adjusting the depth of theembossing of said protuberances,

the steepness of the reinforcement notch (23) by adjusting the greateror lesser depth of said notch,

the steepness of the line marking the start of the transverse notch (24)by adjusting the greater or lesser depth of the notch leading to thismarking of the start of the transverse taper (24),

the mechanical tension “T” (47) of the facing paper (3) by tighteningthe latter to a greater or lesser extent with the help of dedicatedtighteners.

The first device, called a embossing tracker (30), associated with themethod according to the invention appearing in FIG. 1 and detailed inFIG. 3 and FIG. 4 carries out all the phases of the method according tothe invention of berthing and on-the-fly machining on-the-fly of thefacing paper (3) before the latter engages below the mixer (1). Thesesaid machining operations are the embossing of the lines ofprotuberances (20), the embossing of the extensions of line ofprotuberances (28), the coating covering the protuberances (16), thecoating covering the reinforced surface (21), the realization of thereinforcement notches (23), the notching of the lines marking the startof the transverse taper (24), the notching of the tapers connectionlines (26), and the realization of the rough surface (25).

According to the invention, the embossing tracker (30) driven by itsmotor and transmission system (33) catches up and spends a few fractionsof seconds at the same speed as the facing paper (3). Once the embossingtracker (30) is at the same speed as the facing paper (3) the lowertable (31), an integral part of the embossing tracker (30), makes an upand down movement by means of the jacks and guides (34). During its upand down movement the lower table (31) compresses the facing paperagainst the upper table (32), also an integral part of the embossingtracker (30). During this compression of the facing paper (3) the toolsfitted on the lower table (31) and the upper table (32) exert theireffect and therefore locally machine the facing paper (3). Thus thepunches (35) fitted to the upper table (32) and the dies (36) fitted tothe lower table (31) realize the lines of protuberances (20) andaccording to a variant of the method according to the invention theextensions of lines of protuberances (28). Thus the stampers (37) fittedto the lower table (31) and the counter-stampers (38) fitted to theupper table (32) realize the reinforcement notches (23), the linesmarking the start of the transverse taper (24), the tapers connectionlines (26), the pricking of the rough surface (25). More specificallythe inner ridge (39) of the stamper (37) produces the reinforcementnotch, the outer ridge (40) of the stamper (37) produces the linesmarking the start of the taper and the tapers connection lines (26), theneedles (41) of the stamper producing the rough surfaces (25).

Immediately after the embossing and cream-paper marking (3) operations,the nozzles (44) situated between the punches (35) spray onto theprotuberances (16) and onto the reinforced surface (21) the coating (15)the main function of which is to hold and reinforce the protuberances(16).

According to the invention, the embossing tracker (30) in position “02”during the machining of the facing paper (3) rapidly travels back toposition “01”, a new cycle of berthing and machining the facing paper(3) resumes at a step “p” (48) of the previous machining of the facingpaper (3) and thus the cycle then repeats itself.

The motor and transmission system (33) is associated with suitableelectronics, and with the pulse generator (42) which permanentlymeasures the unrolling of the facing paper (3). This motor andtransmission system (33) can thus berth the facing paper at a rapidfrequency (3) and allow at every step “p” (48) the machining operationsnecessary for the method according to the invention.

The calculation of this interval “p” peculiar to the method according tothe invention is presented in the disclosure of the method according tothe invention.

According to a variant of the embossing tracker (30), the punches (35)and the dies (36) allow by their shapes and counter-shapes,protuberances (16) to be realized which are either hemispherical orpyramidal or conical or even half-moon, shaped without these forms beinglimitative.

According to the method of the invention the protuberances (16) areprotected during their passages in the zone between the forming table(5) and the former (7). For this, in the said zone all the roughsections of the forming table (5), all the catch points (17) of theguides and forming rules are removed. Grooves are provided on thespreader (6), this spreader (6) is generally a vibrating table orbeating rollers beat the facing paper (3) in order to spread thehydraulic binder (2) without affecting the protuberances (16) which,passing them in the grooves, pass without being touched by the spreader(6). Thus the said zone between the forming table (5) and the former (7)does not affect the lines of protuberances (20).

The second device realizing the cut at the level of the imprints (19) isconstituted by the imprint detector (18) at a distance “d” from theshears (2) and suitable electronics which, knowing the speed “V” of thecomposite strip (45), orders the shears (11) to cut the composite strip(10) into sections at the level of the double-slope imprint (19).

1-10. (canceled)
 11. A method of continuous production of plaster boardsin which two sheets of cardboard-type paper, one constituting facingpaper and the other gray or backing paper, enclose in a former aplaster-based hydraulic binder creating a composite strip which hardenson two hardening belts and around the edge of which are two taperedstrips for the making-up of the longitudinal tapered edges, the methodcomprising: embossing the facing paper along lines of protuberancestransverse and perpendicular to a direction of unwinding of the facingpaper and projecting below said facing paper, said lines ofprotuberances being produced: over a length equal to the width of theplaster board minus the sum of the widths of the two longitudinaltapers, in a zone situated before the mixer and former, at a high rate,on-the-fly, and with a distance between the lines of protuberancescorresponding to the future length of the plaster board, notching thefacing paper, simultaneously with the notching of the lines ofprotuberances, along two continuous straight lines of reinforcingnotches, said lines of reinforcement notches being realized: on theoutside of the facing paper, on either side of each line ofprotuberances, with the same length as the lines of protuberances,parallel to and centered vis-ac-vis the lines of protuberances,protecting the lines of protuberances against pulling out, catching ordeformation until the crossing of the former, allowing said lines ofprotuberances projecting below the facing paper to cross the former, andto locally reduce the quantity of hydraulic binder enclosed between thefacing paper and the gray or backing paper, allowing said lines ofprotuberances projecting below the facing paper to rest on the twohardening belts, and, locally raising said facing paper and generatingdouble-slope imprints, allowing the double-slope imprints to cross thetwo hardening belts and, cutting the composite strip using the shears atthe level, in the center and in the axis of each of the double-slopeimprints thus created.
 12. The method according to claim 11, wherein allthe insides of the protuberances and the upper and horizontal surfacesof the facing paper between the protuberances and the reinforcingnotches, said surface being called reinforced surface, are covered by alayer of coating, on-the-fly applications of said coating being realizedimmediately after the embossing operation of the lines of protuberances,the coating comprising: increasing the mechanical strength of the linesof protuberances, making the lines of protuberances impermeable, makingthe lines of protuberances tight vis-à-vis the hydraulic binder,guaranteeing a good bonding of the hydraulic binder and the facing paperat the reinforced surface.
 13. The method according to claim 11, whereinthe lines of protuberances are extended at each of their ends over alength equal to the width of the longitudinal tapers by an extension ofthe line of protuberances with protuberances the protuberance height ofwhich decreases as said line of protuberances approaches the outsideedge of the facing paper, said extension of the line of protuberancesduring the crossing of the hardening belts and coming to rest on thetapered strips, the function of said tapered strips being the making-upof the longitudinal tapers.
 14. The method according to claim 12,wherein the lines of protuberances are extended at each of their endsover a length equal to the width of the longitudinal tapers by anextension of the line of protuberances with protuberances theprotuberance height of which decreases as said line of protuberancesapproaches the outside edge of the facing paper, said extension of theline of protuberances during the crossing of the hardening belts andcoming to rest on the tapered strips, the function of said taperedstrips being the making-up of the longitudinal tapers.
 15. The methodaccording to claim 11, wherein the facing paper is premarked by a taperstart marking line, corresponding to a future start of the transversetaper, said taper start line being the same length as and parallel tothe line of protuberances and at a distance from the latter, saiddistance being equal to the sought width “a” of the transverse taper,this premarking involving a light notching of the facing paper andoccurring at the same time as the embossing of the lines ofprotuberances.
 16. The method according to claim 15, wherein the facingpaper is premarked by a tapers connection line corresponding to themeeting of the longitudinal taper and the transverse taper, said tapersconnection line starting from the end of the line marking the start ofthe transverse taper and ending at the line of reinforcing notches at anangle of 45°, said premarking involving a light notching of the facingpaper and occurring at the same time as the embossing of the lines ofprotuberances.
 17. The method according to claim 11, wherein the outsidesurface of the facing paper corresponding to the future transverse taperand situated in the polygon defined by the line of the reinforcingnotch, the line marking the start of the transverse taper and the twotapers connection lines is roughened by pricking, knurling, embossing orby chafing, this stage of the method according to the invention ofrealizing the rough surface occurring at the same time as the embossingof the lines of protuberances.
 18. The method according to claim 11,wherein the height of the transverse taper and the width of thetransverse taper are regulated by adjusting the following parameters:the protuberances height, the steepness of the reinforcing notch, thesteepness of the line marking the start of the transverse taper, and themechanical tension of the facing paper.
 19. An apparatus forimplementing a method of continuous production of plaster boards inwhich two sheets of cardboard-type paper, one constituting facing paperand the other gray or backing paper, enclose in a former a plaster-basedhydraulic binder creating a composite strip which hardens on twohardening belts and around the edge of which are two tapered strips forthe making-up of the longitudinal tapered edges, comprising: embossingthe facing paper along lines of protuberances transverse andperpendicular to the direction of unwinding of the facing paper andprojecting below said facing paper, said lines of protuberances beingproduced over a length equal to the width of the plaster board minus thesum of the widths of the two longitudinal tapers, in a zone situatedbefore the mixer and former, at a high rate, on-the-fly, and respectinga distance between the lines of protuberances corresponding to a futurelength of the plaster board, notching the facing paper, simultaneouslywith the notching of the lines of protuberances, along two continuousstraight lines of reinforcing notches, said lines of reinforcementnotches being realized on the outside of the facing paper, on eitherside of each line of protuberances, with the same length as the lines ofprotuberances, parallel to and centered vis-à-vis the lines ofprotuberances, protecting the lines of protuberances against pullingout, catching or deformation until the crossing of the former, allowingsaid lines of protuberances projecting below the facing paper to crossthe former, and to locally reduce the quantity of hydraulic binderenclosed between the facing paper and the gray or backing paper,allowing said lines of protuberances projecting below the facing paperto rest on the two hardening belts, and, locally raising said facingpaper and generating the double-slope imprint, allowing the double-slopeimprints to cross the two hardening belts and, cutting the compositestrip using the shears at the level, in the center and in the axis ofeach of the double-slope imprints thus created, said apparatuscomprising: a production line for plaster boards in which two sheets ofcardboard-type paper, one constituting facing paper and the other grayor backing paper unwind and enclose in a former a plaster-basedhydraulic binder and constitute a composite strip which hardens on twohardening belts fitted with tapered strips for the making-up oflongitudinal tapers, an embossing tracker situated in a zone just beforethe mixer the functions of which are: berthing on-the-fly the facingpaper at the distance, embossing said facing paper to produce lines ofprotuberances, notching said facing paper to produce lines ofreinforcing notches, embossing said facing paper to produce theextensions of the line of protuberances, notching said facing paper toproduce lines marking the start of the transverse taper and tapersconnection lines, roughening the rough surface corresponding to thefuture transverse taper, and a shearing apparatus situated after thehardening belts and the function of which is to cut the composite stripat the level, in the center and in the axis of the double-slopeimprints.
 20. The apparatus according to claim 19, wherein the embossingtracker is constituted by a lower table situated below the facing paperand an upper counter-table situated above the facing paper, said lowertable being fitted with jacks and guides, dies, stampers, each of saidstampers having an inner ridge and an outer ridge and needles, saidupper table being fitted with punches, a counter-stamper, nozzles forcoating and a pulse generator, both of the two said lower and uppertables being an integral part of the embossing tracker, itself driven bythe motor and transmission system.
 21. The apparatus according to claim19, wherein the shearing apparatus is constituted by shears, an imprintdetector, said imprint detector being situated at the known distancefrom the shears and a shears cut calculator.